Under the Channel / Joining the Tunnel

The first major test of the fledgling Maxibor came in late October 1990 when it was used to survey the 100m probe hole from the leading wall of the British side of the Channel Tunnel. This was from the end of the service tunnel from Dover towards the French service tunnel (the smaller tunnel between the two main tunnels which would contain the rail lines).

It was intended that the results of the survey would provide the final link in a survey "chain" that went back to England then via satellite to France and along the French tunnel. The results would show what final adjustments were needed to get the tunnels to meet as closely as possible.
At the time there could not have been a more high profile project on which to test this survey system.

Richard Braithwaite (Encore Drilling) and James Tweedie (GeoMEM Software), as surveying expert and software developer respectively, were present to run the survey. The computer system (an old Toshiba Laptop and an Epson impact dot matrix printer) were housed in Richards "field box" - a strong self-made box that opened out to form a computer centre.
The surveying process took place over two shifts (16 hours) - and resulted in two surveys that were used to define the borehole path. This was added to the long laser based survey that had guided the tunnel up till then and so the French tunnel could be adjusted to align directly with the English side.

Between shifts
At the end of the first shift all the tunnel workers left the end of the tunnel and made the 10 minute walk to the "shuttle train". Richard and James waited at the end of the tunnel 20 miles out from Dover under the English channel, talking quietly in the silence and becoming very aware of the few thousands tons of "soft" rock above them under further pressure from billions of litres of water. Remarkably, out of the thousands of people involved in the Channel Tunnel Project the first person to appear on the new shift was an old colleague of Richards who he had not seen for over 10 years.
"Of all the tunnels in all the countries in all the world, he walks into mine." (With apologies to "Casablanca")

The pilot borehole had intentionally been inclined slightly up to start with then made to define an arc so that after 100m it was at approximately the same elevation as at the start but was inclined down. This was to allow water with green dye to be contained in the end of the borehole. When the French tunnelling machine intersected the borehole then the shower of "unnaturally" coloured water would alert the tunnellers. This happened a few days after the survey and showed that the two tunnels were almost correct in elevation but required a slight horizontal adjustment to meet up exactly aligned.
The Maxibor had proved its worth in, perhaps, one of the most high profile projects in the world at that time.

After leaving the tunnel Richard and James returned to their lodgings. That night they witnesed an impressive electrical storm over the channel. Perhaps Nature recognising the potential linking of the two land masses.

Just over a month later, on the first of December 1990, the service tunnel breakthrough was made and the British Isles and Europe had a "dry-land" connection for the first time in many tens of thousands of years.